The present invention relates to both a hybrid oven for cooking by both hot air impingement and microwave cooking and a non-hybrid oven for cooking by hot air impingement alone, and more particularly to such an oven which is capable of rapidly cooking food products.
The "fast food" industry is based upon the premise that, due to the anticipated sales volume during peak hours, food can be prepared before an order is placed therefor. As a result, the food is usually delivered to the customer within 30 seconds of the order because the food was already prepared, typically within the last five minutes so that its quality is not degraded. However, this results in substantial inventory loss if customer traffic is less than anticipated, as well as substantial delays if customer traffic is more than anticipated, especially during off-peak hours.
Attempts to deliver "cooked to order" food of high quality within an acceptable time frame have not been entirely successful. Indeed, it is precisely this shortcoming which has prevented the creation of acceptable hot food vending machines (similar in size and concept to the well known soft-drink vending machines) which could turn out national fast food chain quality food from a fully automated machine.
A satisfactory quick-cooking oven must be able to heat or cook--from frozen, refrigerated or ambient temperature states--food products, whether they are already prepared (e.g., frozen fried chicken nuggets), partially prepared (e.g., frozen "par-baked" pizza) or raw (e.g., biscuits, fish), with the process generally being completed in less than 30 seconds. It will be readily appreciated that an oven which can complete the process in 30 seconds can enable food to be sold at twice the rate during peak hours than a machine which requires a minute, whether the oven is disposed in a fast food restaurant or is part of an automatic vending machine. Additionally, there is a threshold to the amount of time most consumers will wait for a food product to be delivered. Although there may be some debate as to what that threshold time limit is, it is clear that far fewer customers will knowingly wait for 90 seconds for delivery of their food than will wait for 30 seconds. This marginal customer group will also result in additional sales.
It will be appreciated that a quick-cooking oven is also desirable for many food items because various characteristics which change during the cooking process (such as texture, flavor, odor and appearance) may be affected in different ways during the cooking process--by which is meant, faster cooking times may in certain instances provide a higher overall quality food product than slow cooking times.
Conventional microwave ovens can deliver large amounts of heat over short periods of time, but result in a "synthetic" product, without browning or crisping. While this may be acceptable for some products, such as baked potatoes, it is generally unacceptable for a wide variety of food products such as pizzas, fried chicken, toast, etc. Conventional air impingement ovens can rapidly cook food products by forcing heated air onto the food surface at high velocities, thus "driving" the heat into the food product. Conventional hybrid ovens, which combine both hot air impingement and microwave cooking techniques, can heat and cook more rapidly than either cooking method individually. However, the known hybrid ovens are either much too slow (for example, requiring a lengthy period of as much as five minutes to cook a frozen pizza) or, if they operate on 220 volts and/or are provided with a substantial warm-up time (frequently 15 seconds or so), they can cook the same food product in a faster but still unacceptably slow period (for example, 90 seconds). The 90 second ovens typically use as heating elements heating coils similar to a hair dryer, which take several seconds to reach peak temperatures and then only heat up the air as it passes over the heating coils. Thus such ovens require a substantial warm-up time to heat the coils to peak temperatures and then additional time to heat up the air already in the oven by passing it over the coils. (It should be kept in mind that the initial batch of hot air leaving the heating coils is rapidly cooled as it mixes with the cold food product and the air already present in the cooking chamber.) While a fast food restaurant will generally have a 220 volt power supply available to it, a vending machine location may have only a 110 volt power supply available to it and thus cannot utilize one of the 90 second ovens which requires a 220 volt power supply. Because heating coils and magnetron(s) which could operate simultaneously on a 110 volt power supply would be of substantially reduced capacity as compared to heating coils and magnetron(s) which require an essentially dedicated 110 volt power supply to operate efficiently, a 220 volt power supply would be required to deliver similar cooking energy in the known hybrid ovens.
Non-hybrid hot air impingement ovens are typically not used in applications which require immediate cooking and delivery to the consumer, since the impinging hot air has only a limited ability to cook the food interior, especially where the product is of substantial dimensions. Even so, the non-hybrid hot air impingement oven of conventional design is subject to many of the same disadvantages as the hybrid oven, and in particular requires several minutes in order to cook the food by hot air impingement alone. These ovens, like the 90 second ovens, require a warm-up time of several seconds in order to reach peak temperatures in the heating coils, and then still more time in order to heat up the air already in the system by passing it over the heating coils.
Accordingly, it is an object of the present invention to provide a quick-cooking oven such as a hybrid oven generally capable of cooking most frozen foods within 30 seconds.
Another object is to provide such an oven which utilizes both hot air impingement and microwave cooking.
A further object is to provide such an oven which is operable on a 110 volt power supply.
It is also an object of the present invention to provide a quick-cooking non-hybrid oven which cooks with hot air impingement only.
It is another object to provide such a quick-cooking non-hybrid oven which is generally capable of cooking most refrigerated food products within one minute.
It is a further object to provide such an oven which is safe, simple and economical to manufacture, use and maintain.